Conductive polymer compositions prepared by incorporating conductive particles of carbon black or graphite are well known in the art. The polymers so prepared include thermoplastics, elastomers, thermosets and blends thereof. (See e.g., U.S. Pat. No. 4,545,926).
Carbon and graphite filled fluorocarbon compositions for electrical applications have also been known for some time. They are primarily used in preference to other conductive polymers when chemically active and/or high temperature environments are to be encountered. Applications in which conductive fluorocarbons containing carbon black and/or graphite are used include current-limiting devices e.g., self-regulating heater cable (U.S. Pat. No. 4,318,881, U.S. Pat. No. 4,624,990 and U.S. Pat. No. 4,545,926), antistatic containers for semiconductor chip processing (J6 1027842A), conductive coating compositions (U.S. Pat. No. 4,482,476, U.S. Pat. No. 4,064,074 and EP 79589), battery electrode constructions (U.S Pat. No. 4,468,362, U.S. Pat. No. 3,676,222, EP 126511A and JA 7016669 R), thermally and electrically conductive caulk (U.S. Pat. No. 4,157,327), antistatic/antifriction sheets for use in tape or film cassettes (U.S. Pat. No. 3,908,570) and conductive filaments (J 58163725A, J 75013957).
However, there are difficulties associated with adding carbon black to fluoropolymers to achieve conductivity. One difficulty is the relatively large and rapid rise that occurs in effective melt viscosity of the blend as carbon black is added. This large and rapid viscosity increase results in more difficult and time consuming processing. At low enough levels of carbon black to be of little influence on effective melt viscosity, the electrical conductivity is usually lost or in a range below that desired. Any means to reduce melt viscosity or reduce the carbon black concentration to lower levels while maintaining the desired conductivity is therefore a very desirable goal.
Higher conductivity can be obtained with graphite fibers as filler instead of carbon black. For example, U.S. Pat. No. 4,163,742 uses 5-50 weight percent graphite fibers and obtains resistivity in the range 0.03 to 6.8 ohm-cm. It is also known that fillers with high thermal conductivity can be added to give a polymer blend with increased thermal conductivity as compared with the unfilled polymer.
Compositions with high electrical conductivity can be used for electromagnetic shielding, as in computer cable, semiconductor chip protection, and satellite components. Compositions with high thermal conductivity can be used in articles such as heat exchanger tubing and heater cable jackets.